Constant pressure mechanism of probe

Abstract

A constant pressure mechanism of a probe for urging the probe in a predetermined direction by virtue of elastic force of a spring is provided. The mechanism comprises a circular pulley rotatably supported around a central axis by an instrument stationary portion, a rotation force urging mechanism for urging the pulley in the predetermined direction, and a first wire adjoining the pulley to the probe. The rotation force urging mechanism comprises a spiral pulley coaxial with and capable of combined rotation with the circular pulley, and a second wire connecting the spiral pulley to the spring. The other end of the spring is connected to the instrument stationary portion. Strict contact pressure of the probe is maintained throughout its motion.

What is claimed is:  
     
       1. A constant pressure mechanism of a probe for unidirectionally urging the probe in a predetermined direction by virtue of elastic force of a spring, comprising: 
       a first pulley rotatably supported around a central axis by an instrument stationary portion;  
       a rotation force urging mechanism for urging the first pulley in a predetermined rotation direction; and  
       a first wire having a first end fixed to the first pulley and a second end joined to the probe,  
       wherein the rotation force urging mechanism includes:  
       a second pulley coaxial with the first pulley and capable of combined rotation therewith; and  
       a second wire having an end fixed to the second pulley, and the spring having one end fixed to the instrument stationary portion with a free end joined to the other end of the second wire;  
       wherein the first pulley and the second pulley are respectively either a circular pulley or a spiral pulley; and  
       wherein a radius “r” and an angle “φ” of polar coordinates of a spiral drawn by the contact point between the spiral pulley and the first or the second wire are represented by the following equations:        r   =       f        (   φ   )       =         K   ·     R   2       Fm            1   +     θ   2                             
        where “f(φ)” represents an function of the rotation angle “φ”;  
       “K” represents spring constant of the spring;  
       “R” represents a radius of the circular pulley;  
       “Fm” represents measurement force of the probe; and  
       “θ” represents a rotation angle of the circular pulley and the spiral pulley.  
     
     
       2. The constant pressure mechanism of a probe according to  claim 1 , wherein the spring is a coil spring. 
     
     
       3. The constant pressure mechanism of a probe according to  claim 1 , wherein the spring is a plate spring. 
     
     
       4. The constant pressure mechanism of a probe according to  claim 1 , wherein the rotation force urging mechanism includes a spiral spring having an end being fixed to the instrument stationary portion and the other end being jointed to the first pulley. 
     
     
       5. The constant pressure mechanism of a probe according to  claim 1 , wherein a counter mechanism is connected to an inner end of the probe.